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Why Are Some People Morning or Night People?


by Kumaraswamy Budur, M.D.

Q. Why are some people morning people and some night people?

A. Scientists think it may just be in our genes.

Normally, the human biological clock coincides with the external clock—or night and day. Therefore, though a slight shift in the biological clock may make them prefer one time of day, most people are able to sleep at night and stay awake during the day without any problems. In other people, though, the biological clock is so out of sync with the external clock that they have what we call delayed or advanced sleep phase syndrome:newsletter-graphic

  • Delayed sleepers (night owls), most commonly adolescents or young adults, are sometimes awake until 2 or 3 a.m. When forced to wake up early, they feel sleepy and tired. They’re often most alert, productive and creative in the evening or late at night.
  • Advanced sleepers (early birds), usually elderly, go to bed early (6 to 9 p.m.) and get up early (2 to 5 a.m.). They typically function well in the mornings and have a hard time staying awake and functioning late in the evening.

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If problems waking up or staying awake interfere with your daily life, a sleep specialist may be able to help.

KUMARASWAMY BUDUR, M.D., is a psychiatrist with The Cleveland Clinic Foundation.


Last updated and/or approved: March 2011.
Original article appeared in fall 2006 former print magazine. Bio current as of that issue. This general health-care information is not meant as individual advice. Please see our disclaimer.
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